Tangalooma

Laptop failure has kept me away from these pages for a few weeks.  Its now going again thanks to Tim – he sold me an old – but working – laptop identical to mine, so I scavenged the best bits of each and now have a pretty good, but old, iBook.

My brother Greg has been on board for the last few days and yesterday we sailed to Straddie – Deanbilla Bay was too jiggly and we moved around to Myora for last night.  And now we are at Tangalooma – it was a great sail here from Myora. The anchorage here is also a bit rolly – the wind is more from the south than I expected.

For those interested in the electric motor and technical stuff read on.

One of the attractive features of electric motors is that, when sailing, the motor spins as the water flows past the prop, and power is fed back into the batteries.  In practise though the speed at which regen occurs is too high.  Today the regen peaked at about 8 amps, at a boat speed of around 11 knots.  Regen starts at a little over 5 knots.  At 5 its zero.  At 7.5 knots its about 3 amps.  between 9 and 10 knots it kicks in about 6 amps of power.

The motor well is open at the bottom and at speed over 9 knots the water really boils around in the well.  So the flow over the prop is anything but streamlined, and so I think there is scope for improvement by attaching a panel to the motor which will nicely seal the bottom of the well, and create a smooth streamline shape above the motor.

At speeds over 10 knots it sounds like cavitation – or some form of aeration – is occuring and the efficiency would not doubt be suffering.

At start of sailing the engine batteries were down 5 amhours from anchoring the night before and getting off the anchor this morning.  The sail to Tangalooma – or at the last hour or so when speed was high enough – put back most of this deficit.  But anchoring was troublesome and we did it three times until i was satisfied with it.  That drew power out of the engine pack so they are now down 15 amphours.

This is my cue to fess up – I bought a cheap genset to top up the batteries until such time as I get more solar power, and improve the regen. Until then I will be be using – gasp – fossil fuel to satisfy my need for power.

Thats all for today.  cheers

–chris